Search results for "RETRIEVAL"
showing 10 items of 1176 documents
Microscopic s-wave optical potential for slow pions scattered by a nucleus.
1989
We have done a microscopic calculation of the {ital s}-wave optical potential for the pion-nucleus system at low energies, 0{le}{ital T}{sub {pi}}{le}100 MeV, using a description based on hadronic degrees of freedom. We have obtained, separately, the real and imaginary parts of the optical potential coming from one-body and two-body processes. We have also separated the imaginary part of the potential associated to absorption and to quasielastic channels. We find that the imaginary part of the absorption channel is independent of the energy (within the range of energies considered here) in agreement with a recent empirical determination. We compare our results with phenomenological potentia…
Alternative large-n limit for QCD and its implications for low-energy nuclear phenomena
1990
The Corrigan-Ramond model for large-{ital N} QCD is analyzed in detail. The spectrum, leading-order results for interactions, and an effective Lagrangian describing large-{ital N} interactions are derived. This Lagrangian, when quantized, provides an effective quantum field theory for mesons and baryons. The applicability of such a theory to low-energy nuclear phenomena is studied. The model has features that distinguish it clearly from standard large-{ital N} QCD.
Constraints on additionalZ′gauge bosons from a precise measurement of theZmass
1990
We analyze the constraints on the mass and mixing of superstring-inspired E{sub 6} {ital Z}{prime} neutral gauge boson that follow from the recent precise {ital Z} mass measurements and show that they depend very sensitively on the assumed value of the {ital W} mass and also, to a lesser extent, on the top-quark mass.
Multi-hadron spectroscopy in a large physical volume
2017
We demonstrate the efficacy of the stochastic LapH method to treat all-to-all quark propagation on a $N_f = 2+1$ CLS ensemble with large linear spatial extent $L = 5.5$ fm, allowing us to obtain the benchmark elastic isovector p-wave pion-pion scattering amplitude to good precision already on a relatively small number of gauge configurations. These results hold promise for multi-hadron spectroscopy at close-to-physical pion mass with exponential finite-volume effects under control.
MeCaSDa and ECaSDa: Methane and ethene calculated spectroscopic databases for the virtual atomic and molecular data centre
2013
Abstract Two spectroscopic relational databases, denoted MeCaSDa and ECaSDa, have been implemented for methane and ethene, and included in VAMDC (Virtual Atomic and Molecular Data Centre, http://portal.vamdc.eu/vamdc_portal/home.seam ). These databases collect calculated spectroscopic data from the accurate analyses previously performed for the electronic ground state of methane, ethene, and some of their isotopologues: 12CH4, 13CH4, and 12C2H4. Both infrared absorption and Raman scattering lines are included. The polyad structures are reported and the transitions are precisely described by their energy, their intensity and the full description of the lower and upper states involved in the …
ElectronicgFactor of Hydrogenlike OxygenO7+16
2004
We present an experimental value for the $g$ factor of the electron bound in hydrogenlike oxygen, which is found to be ${g}_{\mathrm{e}\mathrm{x}\mathrm{p}\mathrm{t}}=2.000\text{ }047\text{ }025\text{ }4\text{ }(15)(44)$. The experiment was performed on a single $^{16}\mathrm{O}^{7+}$ ion stored in a Penning trap. For the first time, the expected line shape of the $g$-factor resonance is calculated which is essential for minimizing the systematic uncertainties. The measurement agrees within $1.1\text{ }\ensuremath{\sigma}$ with the predicted theoretical value ${g}_{\mathrm{t}\mathrm{h}\mathrm{e}\mathrm{o}\mathrm{r}\mathrm{y}}=2.000\text{ }047\text{ }020\text{ }2\text{ }(6)$. It represents a…
Dielectric versus topographic contrast in near-field microscopy
1996
Using a fully vectorial three-dimensional numerical approach (generalized field propagator, based on Green's tensor technique), we investigate the near-field images produced by subwavelength objects buried in a dielectric surface. We study the influence of the object index, size, and depth on the near field. We emphasize the similarity between the near field spawned by an object buried in the surface (dielectric contrast) and that spawned by a protrusion on the surface (topographic contrast). We show that a buried object with a negative dielectric contrast (i.e., with a smaller index than its surrounding medium) produces a near-field image that is reversed from that of an object with a posi…
Anomalous behavior of the second magnetization peak inLa1.81Sr0.19CuO4single crystals: Possible influence of two-band superconductivity
2008
We report an anomalous temperature $T$ variation of the field ${H}_{\text{on}}$ for the onset of the second magnetization peak in ${\text{La}}_{1.81}{\text{Sr}}_{0.19}{\text{CuO}}_{4}$ single crystals with the external magnetic field $H$ oriented parallel to the $c$ axis. While the peak field ${H}_{p}$ has a continuous decrease with increasing $T$, ${H}_{\text{on}}$ exhibits a sudden decrease for $T\ensuremath{\sim}11--15\text{ }\text{K}$. This behavior appears to be related to the particular $T$ dependence of the superfluid density in the case of two-band superconductivity affecting the $T$ variation of the elastic energy of the vortex system at low $H$.
Vortex-glass transition in three dimensions.
1991
We investigate the possibility of a vortex-glass transition in a disordered type-II superconductor in a magnetic field in three dimensions by numerical studies of a simplified model. Monte Carlo simulations at finite temperature and domain-wall renormalization-group calculations at {ital T}=0 indicate that {ital d}=3 is just above the lower critical dimension {ital d}{sub {ital l}}, though the possibility that {ital d}{sub {ital l}}=3 cannot be definitely ruled out. A comparison is made with {ital XY} and Ising spin glasses. The (effective) correlation-length exponent {nu} and dynamical exponent {ital z} are in fairly good agreement with experiment.
Breaking Symmetry Effects on Heavy Tetraquarks
2017
In this contribution we present symmetry arguments that can be applied to study the stability of four-quark systems with two different masses. The role played by different symmetry breaking effects and the non-Abelian algebra of color forces is discussed in detail. In the particular case of hidden-flavor all-heavy four-quark states, QQ (Q) over bar(Q) over bar, the system becomes unstable for standard color-additive models. Differences and similarities between Qq (Q) over bar(q) over bar and QQ (q) over bar(q) over bar configurations are presented. In the latter case, its stability when the mass ratio M/m increases was established almost forty years ago. In the former case, we find a kind o…